We have investigated the photoluminescence mapping characteristics of semi-insulating (SI) InP wafers obtained by annealing in iron phosphide ambience (FeP2-annealed). Compared with as-grown Fe-doped and undoped SI InP wafers prepared by annealing in pure phosphorus vapour (P-annealed), the FeP2-annealed SI InP wafer has been found to exhibit a better photoluminescence uniformity. Radial Hall measurements also show that there is a better resistivity uniformity on the FeP2-annealed SI InP wafer. When comparing the distribution of deep levels between the annealed wafers measured by optical transient current spectroscopy, we find that the incorporation of iron atoms into the SI InP suppresses the formation of a few defects. The correlation observed in this study implies that annealing in iron phosphorus ambience makes Fe atoms diffuse uniformly and occupy the indium site in the SI InP lattice. As it stands, we believe that annealing undoped conductive InP in iron phosphide vapour is an effective means to obtain semi-insulating InP wafers with superior uniformity.
Sn-doped InP wafers were etched by reactive ion beam etching (RIBE) using a gas mixture of at ion energies varying from 100 to 600 eV. We investigated the radiation damage caused by RIBE using various techniques which are sensitive to the near-surface region. The optical and electrical properties of the damaged layer as a function of ion energy were studied by photoluminescence microscopy (PLM), photoluminescence spectroscopy, spectroscopic ellipsometry (SE) and electrochemical capacitance - voltage profiling. The electron channelling pattern technique (ECP) was used to examine the structural disorder. The observed radiation damage was attributed to the formation of phosphorus vacancies indicating preferential loss of phosphorus in the InP. We found optimum etching conditions at an ion energy of 400 eV representing the best trade-off between high etch rate and low radiation damage. The potential of PLM, SE and ECP as fast and non-destructive techniques for quality control in research as well as manufacturing is demonstrated.